This application claims priority under 35 U.S.C. xc2xa7xc2xa7119 and/or 365 to Patent Application Ser. No. 0201975-0 filed in Sweden on Jun. 25, 2002, the entire content of which is hereby incorporated by reference.
The present invention relates to a directly pressed cutting insert for chip removing machining.
The most common hard material in cemented carbide is tungsten carbide, WC. Numerous hard metal grades contain only WC and binder metal. In others, carbides of the metals titan (TiC), tantalum (TaC) and niobium (NbC) are also included. The most common binder metal is cobalt, Co, but also nickel, Ni, occurs. The cemented carbide is a powder mixture built up by carbide particles having a grain size 0.5-10 xcexcm and a binder metal, generally cobalt. The percentage by volume is 5-40% for the binder metal, and 95-60% for the carbides. The manufacture of cemented carbide products can be divided into the steps of:xe2x80x94manufacturing of cemented carbide powder, xe2x80x94pressing, xe2x80x94sintering, xe2x80x94finishing and xe2x80x94possibly coating. At the pressing, the cemented carbide powder is pressed to a solid and thereby obtains its shape. However, it does not obtain the correct dimensions until the subsequent sintering. The pressed bodies of cemented carbide powder have a low strength, approximately the same as chalk. In order to obtain the desired properties, hardness, wear resistance, etc., the material has to be sintered. During the sintering, the length, width and height dimensions of the cemented carbide body decrease. Different hard metal grades have different shrinkage. Today, most indexable inserts are directly pressed to complicated shapes, which are to provide good clamping possibilities, as well as good chip breaking or chip forming.
Today, the known pressing technique includes: (1) a negative die, which produces a blank without clearance (see FIG. 1), (2) a positive die, which produces a blank with clearance and planar surface of uniform width at the edge, and which demands after-treatment by means of grinding, and (3) a positive shearing tool, which produces a blank with clearance and a sharp edge. By xe2x80x9cshearxe2x80x9d, is meant a nominal gap of about 10 micrometer between pressing parts. The drawbacks of the known techniques are that the freedom of choice regarding geometries is limited and that each blank shape is predetermined by the respective pressing tool.
One object of the present invention is to provide a directly pressed cutting insert.
Another object of the present invention is to provide a cutting insert having a varying planar surface.
An additional object of the present invention is to provide a cutting insert that may be directly pressed with great freedom of choice regarding the geometry of the cutting body and the chip breaker in the pressing tool.
The invention relates to a directly pressed cutting insert for chip removing machining which is formed by a pressing force acting in a pressing direction. The insert comprises a top surface, a bottom surface, and edge surfaces interconnecting the top and support surfaces. The top surface comprises a rake face, wherein a cutting corner is formed in an area of an intersection of two of the edge surfaces. The cutting corner comprises a first cutting edge. One of the two edge surfaces comprises a first clearance surface having a first clearance angle and a second clearance surface having a second clearance angle which is greater than the first clearance angle. Both of the first and second clearance surfaces connect to the same first cutting edge. The cutting insert has a negative basic shape, wherein a major part of at least some of the edge surfaces is parallel to the pressing direction.